To construct various rotation-supporting members, a ball bearing which has a seal and is used by being lubricated with grease is widely used. In a known radial ball bearing which has a crown-type retainer and has a seal at both sides thereof, the axial center line of balls is shifted away from the axial center line of the inner ring and the outer ring and to the claw portion side of the crown-type retainer (see patent document 1). As the technique of improving lubricity and extending the life of a ball bearing which has a shield and is used by being lubricated with grease, the use of grease excellent in its heat resistance is known (see patent document 2).
But in the bearings described in the patent documents 1 and 2, there is a limit to the amount of the grease which can be filled in the space inside the bearing. Thus it is difficult to extend the life of the bearings further.
Patent document 1: Japanese Patent Application Laid-Open No. 2002-130305
Patent document 1: Japanese Patent Application Laid-Open No. 2004-352858